# US 10,370,794 B2 · Method for producing paper, and pitch removal agent

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- Number: US 10,370,794 B2
- Document ID: US10370794B2
- Status: Granted
- Kind: B2
- Application number: 15/123,528
- Filed: 2015-03-11
- Published: 2017-03-16
- Granted: 2019-08-06
- Earliest claimed: 2014-03-11
- Assignees: Kurita Water Industries Ltd.; Mitsubishi Chemical Corporation
- Applicants: Kurita Water Industries Ltd.; The Nippon Synthetic Chemical Industry Co., Ltd.
- Inventors: Chigusa Taguchi; Munetoshi Tomita; Hiroki Takeda
- Web page: https://patentgrep.com/patent/US10370794B2

## CPC

- D21C 9/086: {with organic compounds or compositions comprising organic compounds}
- D21B 1/32: of waste paper
- D21B 1/325: {de-inking devices}
- D21C 5/025: {De-inking}
- D21C 5/027: {Chemicals therefor}
- D21C 9/08: Removal of fats, resins, pitch or waxes; {Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching (fats, waxes C11B; natural resins C09F1/00; hemicellulose C08B37/14; purification by mechanical means D21D5/00)}
- D21H 11/14: Secondary fibres (working-up waste paper D21C5/02)
- D21H 17/36: Polyalkenyalcohols; Polyalkenylethers; Polyalkenylesters
- D21H 21/02: Agents for preventing deposition on the paper mill equipment, e.g. pitch or slime control (removal of fats, resins, pitch, or waxes D21C9/08)
- Y02W 30/64: Paper recycling
- D21C: PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21B: FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21H: PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT

## Abstract

Provided is a method for producing paper and a pitch removal agent that can remove pitch efficiently. A pitch removal agent having an average polymerization degree of 300 to 2500, a saponification index of 70 to 88 mol % and satisfying, when the absorbance at a wavelength of 490 nm is designated as y (Abs) and the saponification index as x (mol %), the Numerical Formula (A) below is added to a pulp slurry during production of paper using waste paper in the step of deinking the waste paper by floatation and/or a step earlier: y=−0.0297x+b (A) (wherein, 70≤x≤88 and 2.80≤b≤3.03).

## Claims

### Claim 1

A method for producing paper using waste paper, comprising:
polymerizing a compound in a presence of at least one chain-transfer agent containing an aldehyde, thereby obtaining polyvinyl acetate;
saponifying the polyvinyl acetate, thereby obtaining a polyvinyl alcohol; and
adding, to a pulp slurry in a step of deinking the waste paper by floatation and/or a step earlier, the polyvinyl alcohol having an average polymerization degree of 300 to 2500, a saponification index of 70 to 88 mol %, and an absorbance at a wavelength of 280 nm in an ultraviolet absorption spectrum of its 0.1 mass % aqueous solution of 0.2-1.0 Abs and satisfying, when an iodine absorbance at a wavelength of 490 nm is designated as y (Abs) and the saponification index as x (mol %), the following Numerical Formula (A):
[Numerical Formula 1]
y=−0.0297x+b (A)
(wherein, 70≤x≤88 and 2.80≤b≤3.03).

### Claim 2 (depends on 1)

The method according to claim 1, wherein the iodine absorbance is measured at 25° C.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the absorbance at the wavelength of 280 nm in the ultraviolet absorption spectrum of its 0.1 mass % aqueous solution of 0.2-1.0 Abs indicates double bonds adjacent to terminal carbonyl groups contained in a structure of the polyvinyl alcohol.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the absorbance at the wavelength of 280 nm in the ultraviolet absorption spectrum of its 0.1 mass % aqueous solution is 0.3-0.5 Abs.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the aldehyde is one selected from the group consisting of acetaldehyde, benzaldehyde, propionaldehyde, and n-butyraldehyde.